Electric motor control for shaft positioning systems



Dec. 15, 1953 R. F. WITTERS 2,662,998

ELECTRIC MOTOR CONTROL FOR SHAFT POSITIONING SYSTEMS Filed Jan. 5, 1951 2 Sheets-Sheet 1 SHAFT P SI 3: 2

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N INVENTOR. RoBtRTFW/TTERS N BY N I N w M N ATTORNEY Dec. 15, 1953 R. F. WITTERS 2,662,998

ELECTRIC MOTOR CONTROL FOR SHAFT POSITIONING SYSTEMS Filed Jan. 5, 1951 2 Sheets-Sheet 2 IN VEN TOR.

BY Roan? T F m r 7.0?5

ATTORNEY j Patented Dec. I5, 1953 UNITED STATES PATENT OFFICE ELECTRIC MOTOR CONTROL FOR SHAFT POSITIONING SYSTEMS Robert F. Witters, Cedar Rapids, Iowa, assignor to Collins Radio Company, a corporation of Iowa Cedar Rapids, Iowa,

Application January 5, 1951, Serial No. 204,672

have a constant intermediate frequency stage and this requires a variable oscillator in the receiver which may be adjusted so that the resulting beat with the incoming signal will remain at a .constant frequency. As the local oscillator is varied over its frequency range it is oftentimes desirable to change the components in the radio frequency section of the receiver to tune it to the incoming signal. Thus, it is desirable to gang the local oscillator and the tuning elements in the radio frequency section together.

It is an object of this invention, therefore, to provide control means for tuning elements in the radio frequency section of a receiver which automatically adjusts them to the correct position corresponding to the setting of a local oscillator control shaft.

Another object of this invention is to provide a control circuit which controls a tracking device and which will prevent hunting of the tracking device.

Yetlanother object of this invention is to provide an anti-hunting control device.

A feature of this invention is found in the provision for a control means and a controlled means which has anti-hunting characteristics.

Further objects, features and advantages of this invention will become apparent from the following description and claims when read in view of the drawings, in which:

Figure 1 is a schematic drawing of the control and controlled apparatus of this invention.

Figure 2 is a graph illustrating a control problem; and,

Figure 3 is a detailed schematic drawing of the control and controlling apparatus of this invention.

Referring to Figure 1, an oscillator I has a frequency control shaft II and a control knob I2 is connected to its free end. A pair of switches I3 and I4 are mounted on the shaft II. The switch I3 comprises a circular disc of insulating material I5 and a plurality of conducting segments I0 mounted about its periphery. The segments I6 are insulated and separated from each other and a slide contact I1 is connected to the shaft I I and is movable by the knob I2 to engage In radio receivers it is oftentimes desirable to 7 Claims. (Cl. 318-33) The switch I4 is similar to the switch I3 except that the switch I4 has a smaller number of segments I5 about its periphery. A slide contact I8 engages the segments of the switch It and is movable with the shaft I I. Between the segments I5 of the switches I3 and I I are mounted conducting pins I9 which are engageable with the contacts I? and I8, respectively, when they are between the segments I8. It is to be understood that the width ofthe contacts I I and I8 are such that when they pass from adjacent segments I3 they never touch more than one.

The purpose of the switches I3 and I4 is to allow the oscillator IE to be tuned over a high and low frequency range with the switch I3 corresponding to the low frequency range and the the various segments IS. The disc I4 and the segments I6 do not rotate with the shaft II.

switch I I corresponding to the high frequency range. In the low frequency range the first harmonic of the oscillator output is used and in the high frequency range the second harmonic of the oscillator is used. For example, if it is desired to obtain an output from the oscillator I0'o'ver the range from 15 to 1,000 kilocycles, the low range might extend from 15 to 500 kilocycles and the high band from 500 to 1,000 kilocycles. It is seen that when the second harmonic is used in the high band that the low band will be retraced by the oscillator. However, the second harmonic of the output will be used instead of the first harmonic In a radio receiver wherein the oscillator I0 is used as a local oscillator to obtain a constant intermediate-frequency, components in the radiofrequency section of the receiver must be changed as the incoming signal varies over a Wide range. Particular components of the radio-frequency section will be good over a particular frequency increment so that once they ar chosen they need not be changed until their range is covered. Thus, step tuning of the radio frequency section may be used.

Therefore, control switches I3 and I4 are electrically connected to a motor 2! which has mounted on its output shaft 22 a controlled or selector switch 23 and motor controlling switches 24 and 26. The switch 23' is step tunable to a plurality of positions with these positions corresponding to the various radio-frequency components which must be connected in the receiver input. The controlled switch 23, for example, is movable through positions a through 9 and in each position a different coil will be connected in the radio efrequency section.

The switches 24 and 26 are motor control switches and track the controlling switches I3 and I4. Figure 3 illustrates in greater detail the 3 electrical connections between the controlling switches I3 and I3 and the motor controlling switches 23 and 26.

Figure 2 illustrates the relationship between frequency output of the oscillator and its shaft position. It is to be noted that the shaft position 0 increases with frequency. Over the lowest frequency range, A, the switch 23 will be at position A with the corresponding coil and components for the radio-frequency section of the receiver connected. The switch i3 will be the control switch and the segment lBa will be engaged by contact ll. As the angle 6 is increased by rotation of the knob 12 the second portion, 2, of the curve will be entered and the contact ll will pass from segment 16a, to segment lfib. This causes the switch 23 to move to its second position 13 where the components of the radio-frequency section will be changed to correspond to the new position. After the contact ll has been rotated through its five segments the selector switch 23 will be inthe fifth position with the corresponding components connected in the radio-frequency section. In order to reach a higher frequency, the operator must change from the low to the high range thus connecting his electrical control circuit from switch i3 to switch Hi. If the contact ll is in its uppermost frequency position when this change is made then the operator will have switched to an intermediate position of the high range and thus may tune up or down the band to reach any desired position between the top of the low range and the to of the high range.

Referring to Figure 3, the segment Hil of switch i3 is electrically connected to a contact 23a adjacent the motor control switch 23. Likewise, segment ltb is connected to a contact 231), and so forth, so that there is a contact 28 corresponding to each segment of the switch [3.

The oscillator I0 is mechanically connected to the contact ll of the switch l3 and the contact H is electrically connected to a terminal 29. A two-position switch 3| is movable between terminals 23 and 32. Contact 32 is connected to contact l8 of switch l4. Switch 3| is connected to one side of a relay 33. The opposite side is connected to a positive voltage B+.

The relay 33 controls a movable switch 33 which moves between terminals 33 and 36. The terminal 34 is connected to one side of a voltage supply as, for example, 28 volts, and the switch 33 is connected to the motor 2|. The other side of the motor 2! is connected to contact 36 and a resistor R1. The other side of the resistor R1 is connected to the opposite side of the motor-operating voltage. Thus, when the relay 30 is energized the switch 33 moves to engage the contact 33, thus connecting the motor to the 28 volts supply so that it rotates until the relay 33 is de-energized. When this occurs the switch 33 moves to engage contact 36, thus shorting the armature of the motor and dynamically breaking the motor to a standstill.

The motor-control switches 24 and 26 are grounded by lead 31 and the switch 24 is formed with a cutaway portion 38 which prevents any of the contacts 28 from touching the switch 24 when the particular contact is radially aligned with the opening 38. Thus, as shown in Figure 3, the portion 38 is adjacent the contact 2811 and since the contact ll of switch l3 engages segment 160, the relay 30 will be energized and the motor 21 will run and drive the switch 24 and selector 23 until the portion 38 is adjacent the contact 280. It is seen that the relay cir-' cuit is completed from ground through the lead 31 to the switch 24, hence from contact 280 to segment E60, then through the contact I! and the switch 3| to the energizing voltage of the relay 30.

When the switch 23 is moved by the motor 2|, the relay circuit will be broken when the portion 38 is adjacent the contact 280. The switch 24 will not move as long as the contact I? engages the segment l3 electrically connected to the contact 23 adjacent the portion 38. Thus the switch 23 will remain in its C position until the contact IT engages segment [6b or ltd. The radio frequency components controlled by the switch 23 are chosen so as to overlap slightly so that as the oscillator moves the short distance between segments the radio frequency components will still be good. It is seen that the switch I3 controls the A, B, C, D and E positions of motor control switch 23 and selector switch 23.

The switch it controls the F and G positions of motor control switch 24 and selector switch 23. When it is desirable to change to the high frequency position the switch Si is moved to engage the contact 32, thus connecting switch M into the motor control circuit while disconnecting switch i3. Switch I4 is formed with two segments 39 and 399 which are engageable by contact H3. The segment 39f is electrically connected to a contact 28] adjacent switch 25 and the segment 39g is electrically connected to contact 289 of switch 2 3. Thus, the motor control circuit comprises the lead 31 from ground to the switch 24, hence through the contacts 28 or 28g to segments 39 or 399, through contact E8 to the switch 3| and to the relay 30. If the contact i8 engages segment 39! the motor 2i will run until the portion 38 is adjacent contact 28f. Selector switch 23 will then be in the F position with the corresponding radio frequency components connected.

It is to be understood that the second harmonic of oscillator H! is being used when the switch 3i is moved to engage contact 32 and for this reason the switch 14 retraces the angular positions of the switch l3. However, because the switch i3 has been disconnected by the switch 3 l, only the switch M will control.

It is to be noted that if the apparatus was operating in the high frequency position and then switched to the low frequency position by moving the switch 3! from contact 32 to 29, it would be possible for the contact H to not touch any segments l6, and thus, the previously explained operation would not occur. This is true because there would be no completed motor control circuit to the contact ll from the segment 16. Therefore, the contacts 19 are placed between each segment is and are electrically connected to contacts on the second motor control switch 23. The contact between segments [6a and 13b is designated as 13a and is electrically connected to contact Ma adjacent switch 26. Likewise, contact [9b is between segments lfib and H50 and is connected to contact Nb of switch 26. Ther is no contact I9 between segments I66 and i611, and contact ile is not connected to the switch I3. The switch I l has a contact 42f between segments 33] and 399 which is connected to contact M of switch 26. Contact My is not connected to switch I l. The switch I4 is made of conducting material and is formed with two arcuate portions 43 and 44 which are adaccaoos jacent each other so as to disconnect adjoining contacts 4| from the switch 26. The switch 26 is grounded by the lead 31.

Thus, it is seen that the contacts [9a through l9cZ and Hi prevent a null position from being obtained when the switch 3! is moved from contact 29 to 32, or vice versa. The arcuate portions 43 and it are formed in the switch 26 so that it is inoperative as long.as the contacts I! or 18 are merely being moved from adjacent segments. Since the switches may be rotated clockwise or counterclockwise it requires two open circuit positions for satisfactory operation. The switch 26 is mechanically connected to the switch 24 and moves with it. Thus, the arcuate portions 43 and will present open circuits during change from adjacent segments on either switches is and it. It is only when a change is made from the higlto low, or low to high positions that a circuit might be completed through switch 26. The circu will be completed through switch 23 then only if the contact l? or it which is connected falls etween segments or 39.

It is seen that this invention provides a contr-ol circuit which has anti-null features and step controls a plurality of elements in response to a continually movable control switch.

Although the invention has been described with respect to preferred embodiments thereof, it is not to be so limited as changes and modifications may be made therein which are wi cm the full intended scope of the invention as defined by the appended claims.

I claim:

1. Anti-null apparatus for preventing a null position being obtained while switching from a first to a second control switch formed v a plurality of segments about their periphery a rotary contact engageable therewith and said contacts being narrower than the distance be tween adjacent segments comprising, a plurality of contacts between said segm nts engageable by said rotary contacts when are between segments, a motor control circuit comprising a pair of motor control switches and having a plurality of peripherally engaging contacts adjacent thereof with each contact adjacent the first of said motor control switches electrically connected to a segment on the first and second control switches, each of said peripheral contacts on said second motor control switch electrically connected to the contacts between segments on said first and second control switches, and said motor control circuit connected to the rotary contact of the first or second control switch.

2. A control circuit comprising first and second control switches formed with a plurality of segments about their periphery and a contact between adjoining segments, and a rotary contact en ageable with said contacts and segments, first and second motor control switches with a plurality of contacts engageable therewith, the contacts engageable with said first motor control switch connected to the segments of said first and second control switches, the contacts engageable with said second motor control switch connected to the contacts between adjoining segments of the first and second control switches, a control means connected to the rotary contacts of said first and second control switches, driving means mechanically connected to first and second motor control switches, said first motor control switch formed with an open circuit position, said second motor control switch formed with a pair of adjacent open circuit positions, a

6 selector switch connectible to the rotary contacts of said first or second control switches, m0- tor actuating means connected to said selector switch and connecting and disconnecting the motor to a power supply in response to actuation of the controlled and motor control switches.

3. Control apparatus comprising, a pair of control switches each of which have rotary contacts that are mechanically connected together, a plurality of segments mounted about the peripheries of each of said control switches, a contact mounted between each pair of said segments, the rotary contacts of said switches engageable, respectively, with a frequency range switch, motor control means connected to said frequency range switch, a pair of motor control switches mechanically connected to said motor and formed vith a plurality of contacts about their periphcries, the contacts about the periphery of the first motor control switch connected to the segments on the first and second control switches, the contacts about said second motor control switch connected to the contacts between the segments of said first and second control switches, a selector means mechanically connected to said motor, and said motor control switches connected to ground.

4. Means for preventing a null position being obtained while switching a control apparatus from a high to a low frequency position comprising, a high frequency control switch and a low frequency control switch, each having a plurality of segments about their peripheries and a rotary contact engageable therewith, and a contact between each pair of said segments, a selector switch engageable with the rotary contact of said high or low frequency control switch, motor actuating means connected to said selector switch, a pair of motor control switches, a motor mechanically connected to said motor control switches, a plurality of contacts about the peripheries of said motor control switches with said contacts about the first motor control switch connected to the segments of the first and second control switches, and the contacts about the periphery of the second motor control switch connected to the contacts between segments of the first and second control switches, said motor control switches connected to ground, the rotary contacts of said control switches mechanically connected together, and controlled apparatus mechanically connected to said motor.

5. Control apparatus which can not be placed in a null position comprising, a pair of control switches which have rotary contacts mechanically connected together, a motor control circuit connectible respectively to one of said rotary contacts, a plurality of segments about each of said control switches, a plurality of contacts between segments of said control switches, a motor mechanically connected to control apparatus, a pair of motor control switches mechanically connected to said motor, a plurality of contacts about the first motor control switch with each contact electrically connected to a segment about the first and second control switches, a plurality of contacts about the second motor control switch with each contact electrically connected to the contacts mounted between segments on said first and second control switches, said first motor control switch formed with an arcuate portion, said second motor control switch formed with a pair of adjacent arcuate portions, and said first and second motor control switches connected to ground.

6. Control apparatus comprising, a pair of confirst and second control switches and electrically connected to contacts mounted about the periphery of the first motor control switch, a plurality of contacts mounted between segments of the first and second control switches and connected to contacts mounted about the periphery of the second motor control switch, said motor control switches connected to ground, said first motor control switch formed with an arcuate portion in its periphery, and said second motor control switch formed with a pair of adjacent arcuate portion in its periphery.

7. An anti-null control apparatus comprising, a pair of control switches, a pair of motor control switches, a motor mechanically connected to said motor control switches and controlled apparatus, motor actuating means connected to said control switches, said control switches electrical ly connected to said motor control switches, a plurality of segments about the first and second control switches, a plurality of contacts about the first motor control switch with each contact connected to a. segment about the control switches, a plurality of contacts between the segments of the control switches and a plurality of contacts about the second motor control switch connected to the contacts btween segments, and rotary contacts on the first and second control switches mechanically connected together and connectible to the motor actuating means.

ROBERT F. WITTERS.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,210,426 Noack Aug. 6, 1940 2,420,026 Yardeny May 6, 1947 2,42j739 Yardeny June 1, 1948 2,455,901 Yardeny Dec. 7, 1948 2,475,217 Bernas July 5, 1949 2,493,844 Yardeny Jan. 10, 1950 2,553,069 Unk et al May 15, 1951 

